The present invention relates to an optical distance measuring sensor that detects the presence of an object to be measured in a prescribed range and measures a direction in which the object is located and a distance to the object. The present invention also relates to a self-propelled cleaner equipped with the optical distance measuring sensor. The present invention also relates to an air conditioner equipped with the optical distance measuring sensor.
Conventionally, ultrasonic sensors, reflection type infrared sensors, infrared distance measuring sensors and so on have been used as sensors intended to detect objects.
Ultrasonic sensors have a wide viewing angle and a long detecting distance, but cannot detect soft objects (futons, blankets, curtains, sofas and so on) because they absorb sound waves. Also, the ultrasonic sensors cannot detect a direction in which an object is located.
Reflection type infrared sensors have a simple structure because they detect reflection of infrared light emitted from a sensor. However, the detection distance varies depending on the color of an object to be detected, so that detected results are unstable due to influence of the color of the object to be detected.
As shown in FIG. 11, a distance measuring sensor using infrared rays is equipped with a light emitting element 101 and a photodetector 103. An object B to be measured is irradiated with infrared rays from the light emitting element 101. Reflected light from the object B is received by the photodetector 103, and a direction in which the object B is located and a distance to the object B are measured (e.g., Japanese Patent Publication No. 5-312948 A).
The distance measuring sensor using infrared rays can accurately detect the distance to the object B because it is hardly influenced by the color of the object B.
However, in the distance measuring sensor using infrared rays, a detection viewing angle is as narrow as ± several degrees because beams emitted from the light emitting element 101 are narrowed. Further, one-beam type sensors, namely sensors having only one light emitting element 101 cannot detect the direction in which the object B to be measured is located. In order to detect this direction, it is required to use a plurality of distance measuring sensors resulting in an increase in size.
It is also possible to generate multi-beams in one distance measuring sensor by using one light emitting-side lens and a plurality of light emitting elements. However, as beams from the light emitting elements become more distant from an optical axis of the lens, a light spot formed on the object to be measured blurs and enlarges due to aberration, thus affecting measurement accuracy. Therefore, the feasible viewing angle is as small as about 30°.